How to Use a Calculator Effectively in Physics Exams

A scientific calculator is essential for IGCSE Physics. Knowing how to use it efficiently prevents careless errors that cost marks.

Before the exam

1. Check your calculator is on the approved list (non-programmable, non-graphical).
2. Replace the battery before exam season.
3. Make sure it is set to degrees mode (not radians) for any trigonometry questions.

Entering calculations correctly

Order of operations

Calculators follow BIDMAS/BODMAS. If your equation has a fraction, use brackets to group the numerator and denominator separately.

Example: to calculate (25 minus 10) / (3 x 2), enter: (25 - 10) / (3 x 2) = 2.5

If you enter 25 - 10 / 3 x 2 without brackets, the calculator gives 25 - (10/3) x 2 = 18.33, which is wrong.

Powers and roots

• For squared: use the x-squared button. Example: 4.2 squared = 17.64
• For cubed: use the x-to-the-power button then 3.
• For square root: use the root button.
• For cube root: many calculators have a dedicated button, or use x-to-the-power (1/3).

Standard form

To enter 3.0 x 10 to the power 8, use the EXP or x10 button: 3.0 [EXP] 8. Do NOT type 3.0 x 10 [EXP] 8 (this gives 3.0 x 10 x 10 to the 8, which is ten times too large).

The sign button

For negative numbers, use the +/- or (-) button, not the subtraction button.

Common calculator errors in physics

1. Forgetting brackets in fractions. Always bracket the entire numerator and the entire denominator.
2. Squaring the wrong quantity. In KE = 0.5mv squared, only the velocity is squared. Enter: 0.5 x mass x velocity x velocity, or 0.5 x mass x (velocity squared).
3. Standard form entry. Using x10 and EXP together gives an answer 10 times too large or too small.
4. Rounding too early. Keep intermediate values in the calculator memory. Only round the final answer.
5. Degrees vs radians. Check the display shows “DEG” for any sine, cosine, or tangent calculation.

Using calculator memory

Store intermediate results using the memory (M+) or ANS button rather than writing down a rounded value and re-entering it. This preserves precision.

Checking your answer

After calculating, ask: does this answer make sense? A car speed should be tens of m/s, not thousands. A person’s weight should be hundreds of newtons. A resistance should be a reasonable number of ohms. If the answer seems unreasonable, re-enter the calculation.